It is mandated to submit financial statements in a form of an XBRL (eXtensible Business Reporting Language) document to the financial services agency. XBRL is an XML (eXtensible Markup Language)-based language providing a standard so that various types of financial reporting information can be generated, circulated, and utilized. An XBRL document is, for instance, a document about a financial accounting report described in XBRL.
XBRL data used in generating an XBRL document is not always of high quality. XBRL data that is input is typically subjected to, in addition to validation in terms of XML or XBRL syntax and format validity, validation based on financial implications and consistency of data items. The validation based on financial implications and consistency of data items can be regarded as validation serving to support an auditing function. XBRL formula is provided as a technique that can be utilized in performing such validation. XBRL formula is a description language that defines rules for performing validation and calculation on XBRL data content. Specifically, a validation process validates input XBRL data against a plurality of validation rules described in XBRL formula.
For instance, audit regulatory agencies or the like may receive XBRL data from a general business cooperation and perform an audit. A validation process checks quality of XBRL data, which is regularly input, against validation rules described in XBRL formula. Thereafter, data processing is performed on the checked XBRL data. The audit is desirably completed within a certain period.    Patent Literature 1: International Publication Pamphlet No. WO 2011/089683
However, the number of pieces of input XBRL data is in an increasing trend. Hence, a validation process based on validation rules described in XBRL formula tends to be time consuming. Data items to be validated against an individual validation rule often make up only a small portion of all input XBRL data pieces. For an individual validation rule, it is desirable that XBRL data pieces containing data items to be validated against the validation rule are extracted rapidly.